uniapp小程序刮刮乐抽奖

 使用canvas画布画出刮刮乐要被刮的图片，使用移动清除画布。

当前代码封装为刮刮乐的组件；

vue代码： 

<template><view class="page" v-if="merchantInfo.cdn_static"><image class="bg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/page_bg.png'" mode="aspectFill"></image><view class="content"><view class="logo"><image :src="merchantInfo.logo" mode="heightFix"></image></view><view class="title"><image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/title.png'" mode="heightFix"></image></view><view class="notification"><view></view><text>每日刮卡抽好礼</text><view></view></view><view class="box"><image class="scrapingBg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/scrapingBg.png'"></image><view class="scrapingBox"><view class="scrapingBoxContent"><!-- 奖品名称 --><!-- <view>{{ prizeTitle || "" }}</view> --><!-- 奖品图片 --><image :src="merchantInfo.cdn_static + prizeUrl"></image><canvas :style="{'width':width+'px','height':height+'px'}" style="position: absolute; top: 0;" canvas-id="myCanvas" id="myCanvas" @touchstart="touchstart" @touchend="touchend" @touchmove="touchmove"></canvas></view></view></view><view class="count"><view class="tip">您今天还有<text>{{total}}</text>次抽奖机会</view></view><view class="btns"><view class="btn" @click="getRule"><image class="btnImg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/rule.png'"></image><view class="btnConent"><image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/ruleIcon.png'"></image><text>查看规则</text></view></view><view class="btn" @click="getResult()"><image class="btnImg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/prize.png'"></image><view class="btnConent"><image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/prizeIcon.png'"></image><text>兑换福利</text></view></view></view></view><view class="win" v-if="rule_show"><scroll-view scroll-y class="win_box .win_box_bg"><mp-html :content="luckDrawInfo.rule" /></scroll-view><text class="iconfont iconcolseIcon theme-font-white" @click="rule_show=false"></text></view><view class="win" v-if="result_show"><view class="win_box1"><image class="win_bg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/result_bg.png'" mode=""></image><view class="win_content"><view class="win_tips theme-font-white">{{currentPrize.desc}}</view><view class="win_title">{{currentPrize.title}}</view><view class="win_btn" @click="choiseAddress()">{{currentPrize.is_address==1?'选择地址':'确定'}}</view></view></view></view><view class="win" v-if="prize_show"><view class="win_tit theme-font-white">我的奖品</view><view class="win_box2"><view class="items"><view class="left i_title">奖品</view><view class="right i_title">中奖时间</view></view><scroll-view scroll-y class="list"><view class="item" v-for="(item,index) in list" :key="index"><view class="left">{{item.lottery_prize_title}}</view><view class="right" v-if="item.is_address==1&&!item.address_id"><view class="r_btn"  @click="choiseAddress1(item)">去领奖</view></view><view class="right" v-else>{{item.created_time}}</view></view></scroll-view></view><text class="iconfont iconcolseIcon theme-font-white" @click="prize_show=false"></text></view></view></template><script>import { luckDrawInfo } from '@/api/luckDraw.js';import colors from '@/mixins/color';export default {mixins: [colors],data() {return {//https://cdn.dev.scrm.juplus.cn/InQLzDLoAl2S9LyNJUXQ45gpA.pngmask: true,wtf:true,luckDrawInfo: {},rule_show:false,result_show:false,prize_show:false,total:0,currentPrize:{},list:[],id: "",prizeTitle: "",prizeUrl: "",filePath: "",ctx: null,width: 0,height: 0,disabled: false, // 是否禁止刮卡readyState: false, // 是否开始绘制endState: false, // 结束刮卡状态watermark: '刮一刮', // 水印文字watermarkColor: '#c5c5c5', // 水印文字颜色watermarkSize: 14, // 水印文字大小title: '刮一刮开奖', // 提示文字titleColor: '#888', // 提示文字颜色titleSize: 24, // 提示文字大小startX: 0, // 触摸x轴位置startY: 0, // 触摸y轴位置touchSize: 30, // 触摸画笔大小percentage: 50, // 刮开百分之多少的时候开奖}},props: {userId: {type: [Number,String]},type:{type: [Number,String]}},//渲染完了mounted() {this.id = this.userId;this.init();this.$nextTick(() => {let content = uni.createSelectorQuery().in(this).select(".scrapingBoxContent");content.boundingClientRect((data) => {this.width = data.width;this.height = data.height;this.ctx = uni.createCanvasContext('myCanvas', this);uni.getImageInfo({src: this.merchantInfo.cdn_static + 'statistics/luckDrawImg/scratchcard/scratchingBefore.png',success: (res) => {this.filePath = res.path;this.drawInit();}})}).exec()})},	methods: {drawInit(imgUrl) {this.endState = false;this.readyState = false;this.ctx.clearRect(0, 0, this.width, this.height); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。// this.ctx.setFillStyle('#ddd'); // 填充颜色// this.ctx.fillRect(0, 0, this.width, this.height); // 填充区域（x,y,宽,高）/*** 绘制文字水印*/// var width = this.watermark.length * this.watermarkSize;// this.ctx.save(); // 保存当前的绘图上下文。// this.ctx.rotate(-10 * Math.PI / 180); // 以原点为中心，原点可以用 translate方法修改。顺时针旋转当前坐标轴。多次调用rotate，旋转的角度会叠加。// let x = 0;// let y = 0;// let i = 0;// while ((x <= this.width * 5 || y <= this.height * 5) && i < 300) {// 	this.ctx.setFillStyle(this.watermarkColor); // 填充颜色// 	this.ctx.setFontSize(this.watermarkSize); // 设置字体的字号// 	this.ctx.fillText(this.watermark, x, y); // 填充的文本（文字，x，y）// 	x += width + width * 1.6;// 	if (x > this.width && y <= this.height) {// 		x = -Math.random() * 100;// 		y += this.watermarkSize * 3;// 	}// 	i++;// }// this.ctx.restore(); // 恢复之前保存的绘图上下文。/*** 绘制标题*/// this.ctx.setTextAlign("center"); // 用于设置文字的对齐// this.ctx.setTextBaseline("middle"); // 用于设置文字的水平对齐// this.ctx.setFillStyle(this.titleColor); // 填充颜色// this.ctx.setFontSize(this.titleSize); // 设置字体的字号// this.ctx.fillText(this.title, this.width / 2, this.height / 2); // 填充的文本（文字，x，y）/*** 绘制图片*/ this.ctx.drawImage(this.filePath, 0, 0, this.width, this.height); this.ctx.draw(); // 将之前在绘图上下文中的描述（路径、变形、样式）画到 canvas 中。this.readyState = true; // 完成绘制},// 手指触摸动作开始touchstart(e) {if (this.disabled || this.endState) {return;}this.startPlay();this.startX = e.touches[0].x;this.startY = e.touches[0].y;},// 手指触摸后移动touchmove(e) {if (this.disabled || this.endState) return;if (!this.prizeTitle) return;if (!this.prizeUrl) return;this.ctx.clearRect(this.startX, this.startY, this.touchSize, this.touchSize); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。this.ctx.draw(true); // false:本次绘制是否接着上一次绘制，true:保留当前画布上的内容//记录移动点位this.startX = e.touches[0].x;this.startY = e.touches[0].y;},// 手指触摸动作结束touchend(e) {if (this.disabled || this.endState) {return;}// 返回一个数组，用来描述 canvas 区域隐含的像素数据，在自定义组件下，第二个参数传入自定义组件实例 this，以操作组件内 <canvas> 组件。uni.canvasGetImageData({canvasId: 'myCanvas',x: 0,y: 0,width: this.width,height: this.height,success: (res) => {console.log(res);let pixels = res.data;let transPixels = [];for (let i = 0; i < pixels.length; i += 4) {if (pixels[i + 3] < 128) {transPixels.push(pixels[i + 3]);}}var percent = (transPixels.length / (pixels.length / 4) * 100).toFixed(2);if (percent >= this.percentage) {this.scrapingSuccess();}},fail: (e) => {console.log(e);},}, this);},// 成功，清除所有图层scrapingSuccess(e) {if (this.endState) {return;}this.endState = true;this.ctx.moveTo(0, 0); // 把路径移动到画布中的指定点，不创建线条。用 stroke() 方法来画线条。this.ctx.clearRect(0, 0, this.width, this.height); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。this.ctx.stroke(); // 画出当前路径的边框。默认颜色色为黑色。this.ctx.draw(true);// 弹出奖品setTimeout(()=>{this.result_show = true;this.drawInit();this.wtf = true;this.prizeTitle = "";this.prizeUrl = "";},800)},init(){if(this.userInfo){this.getInfo()}else{setTimeout(()=>{this.init()},500)}},getInfo(){luckDrawInfo.getDetail({id:this.id}).then(res => {this.luckDrawInfo=res.datathis.total=res.data.my_can_numthis.action('lottery',this.id,0,2,this.luckDrawInfo.title,'','lottery')})},choiseAddress(){this.currentPrize.is_address==1?uni.navigateTo({url:'/pages/address/address'}):''this.result_show=false},choiseAddress1(data){this.currentPrize=datauni.navigateTo({url:'/pages/address/address'})this.prize_show=false},setAddress(id){luckDrawInfo.setAddress({address_id:id,history_id:this.currentPrize.history_id||this.currentPrize.id}).then(res => {uni.showToast({title:"地址设置成功",icon:'none'})})},getRule(){this.scrapingSuccess();setTimeout(()=>{this.rule_show = true;},800)},getResult(){// if(!this.wtf){// 	return false// }this.scrapingSuccess();luckDrawInfo.getResult({lottery_id:this.id}).then(res => {this.list=res.data.datathis.prize_show=true})},// 点击开始,请求接口抽奖startPlay(index) {if(this.luckDrawInfo.is_register==1&&!this.userInfo.type){uni.navigateTo({url:'/pages/login/login'})return false}if(this.luckDrawInfo.is_form==1&&this.luckDrawInfo.user_form_count==0){uni.navigateTo({url:'/pages/form/form?id='+this.luckDrawInfo.form_id+'&type_id=' + this.id + '&type=lottery'})return false}if(!this.wtf){return false}// 活动未开始或活动已结束let startTimeMs = new Date(this.luckDrawInfo.start_time).getTime();let endTimeMs = new Date(this.luckDrawInfo.end_time).getTime();let nowTimeMs = new Date().getTime();if (nowTimeMs < startTimeMs) {uni.showToast({icon: "none",title: "活动未开始"})return false;}if (nowTimeMs > endTimeMs) {uni.showToast({icon: "none",title: "活动已结束"})return false;}this.mask = false;this.wtf = false;luckDrawInfo.run({id:this.id}).then(res => {this.currentPrize = res.data;this.total = res.data.row_lottery_new.my_can_num;this.prizeTitle = res.data.title;this.prizeUrl = res.data.img;}).catch(err => {this.wtf = true;});}}}
</script><style scoped lang="scss">@import 'index.scss';/**/
</style>

scss代码：

.page{width: 750rpx;height: 100vh;position: relative;
}.bg{width: 750rpx;height: 100vh;
}.content{width: 750rpx;min-height: 100vh;height: 1448rpx;position: absolute;top: 0;left: 0;
}.logo{height: 60rpx;display: flex;justify-content: center;margin-top: 90rpx;image{height: 60rpx;}
}.title{height: 254rpx;display: flex;justify-content: center;margin-top: 20rpx;image{width: 640rpx;height: 254rpx;}
}.notification{width: 370rpx;height: 56rpx;display: flex;justify-content: space-between;align-items: center;margin: -60rpx auto 0 auto;view{width: 26rpx;height: 4rpx;background-color: #fff;}text{font-size: 38rpx;font-family: PingFangSC-Medium, PingFang SC;font-weight: 500;color: #FFFFFF;}
}.box{width: 658rpx;height: 422rpx;margin: 110rpx auto 0 auto;position: relative;.scrapingBg{width: 100%;height: 100%;}.scrapingBox{width: 100%;height: 100%;position: absolute;left: 0;top: 0;box-sizing: border-box;padding: 52rpx 62rpx;.scrapingBoxContent{width: 536rpx;height: 318rpx;z-index: 2;position: relative;image{width: 100%;height: 100%;}view {width: 100%;height: 100%;display: flex;justify-content: center;align-items: center;font-size: 100rpx;color: #1B9AF9;text-shadow: 0px 4px 8px rgba(149,216,255,0.5);}}}
}.count{display: flex;justify-content: center;margin-top: 44rpx;.tip{font-size: 28rpx;font-family: PingFangSC-Medium, PingFang SC;font-weight: 500;color: #777777;text{color: #0039AF;}} 
}.btns{display: flex;align-items: center;justify-content: space-between;margin-top: 26rpx;
}.btn{width: 376rpx;height: 166rpx;position: relative;.btnImg{width: 100%;height: 100%;}.btnConent{width: 100%;position: absolute;top: 50%;transform: translateY(-100%);display: flex;justify-content: center;align-items: center;image{width: 42rpx;height: 42rpx;margin-right: 12rpx;}text{font-size: 42rpx;font-family: PingFangSC-Medium, PingFang SC;font-weight: 500;color: #FFFFFF;}}}.win{width: 750rpx;height: 100vh;background: rgba(0, 0, 0, 0.8);position: fixed;top: 0;left: 0;z-index: 2;display: flex;flex-direction: column;align-items: center;justify-content: center;
}.win_box{width: 662rpx;height: 60%;padding: 40rpx;box-sizing: border-box;border-radius: 24rpx;
}.win_box_bg{background: #C3E5FE;
}.bg3{background: #C3E5FE;
}.iconcolseIcon{font-size: 58rpx;margin-top: 98rpx;
}.win_box1{width: 630rpx;height: 922rpx;position: relative;
}.win_bg{width: 630rpx;height: 922rpx;
}.win_content{width: 630rpx;height: 922rpx;position: absolute;left: 0;top: 0;display: flex;flex-direction: column;align-items: center;
}.win_tips{font-size: 48rpx;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;margin-top: 290rpx;
}.win_title{font-size: 48rpx;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;color: #FE6631;margin: 170rpx 0;
}.win_btn{width: 280rpx;height: 80rpx;line-height: 80rpx;text-align: center;background: #FFE047;border-radius: 46rpx;font-size: 32rpx;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;color: #13112C;
}.win_tit{font-size: 48rpx;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;margin-bottom: 32rpx;
}.win_box2{width: 662rpx;height: 900rpx;background: #FFFFFF;border-radius: 24rpx;display: flex;flex-direction: column;
}.items{width: 662rpx;height: 108rpx;background: #C3E5FE;border-radius: 24rpx 24rpx 0rpx 0rpx;display: flex;align-items: center;flex-shrink:0
}.left,.right{width: 50%;text-align: center;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;
}.i_title{font-size: 36rpx;
}.list{height: 792rpx;padding-bottom: 20rpx;overflow: hidden;
}.item{width: 662rpx;height: 88rpx;display: flex;align-items: center;justify-content: space-around;
}.item:nth-child(2n){background-color: #F4F4F4;
}.r_btn{width: 160rpx;height: 60rpx;line-height: 60rpx;text-align: center;background: #FFC659;border-radius: 46rpx;font-family: SourceHanSansSC-Medium, SourceHanSansSC;font-weight: bold;font-size: 32rpx;margin:0 auto;
}

效果: